The present invention relates to a stationary vane for use in the turbine section of a gas turbine. More specifically, the present invention relates to the cooling of the inner shroud portion of a gas turbine vane.
A gas turbine employs a plurality of stationary vanes that are circumferentially arranged in rows in a turbine section. Each vane is comprised of an airfoil section formed between inner and outer shrouds. Since such vanes are exposed to the hot gas discharging from the combustion section, cooling of these vanes is of utmost importance. Typically, cooling is accomplished by flowing cooling air through radially oriented passages, such as forward and aft passages, formed inside the vane airfoil.
A portion of the cooling air flowing through the aft airfoil passage is typically discharged through cooling air holes in the trailing edge of the airfoil. Another portion of the cooling air flowing through the aft passage, as well as the cooling air flowing through the forward airfoil passage, is typically discharged from the vane through the inner shroud and enters a cavity located between adjacent rows of rotor discs. The cooling air in the cavity serves to cool the faces of the discs.
In the past, a portion of the cooling from the cavity between the discs has sometimes been used to cool the inner shroud by impinging cooling air against the shroud surface or flowing cooling air through passages in the body of the shroud. Unfortunately, traditional schemes have not made optimum use of this cooling air. Although such cooling air eventually enters the hot gas flowing through the turbine section, little useful work is obtained from the cooling air, since it was not subject to heat up in the combustion section. Thus, to achieve high efficiency, it is crucial that the cooling air be effectively utilized so as to minimize the amount of cooling air used.
It is therefore desirable to provide a scheme for efficiently cooling the inner shroud of a gas turbine vane.